bonestorm doesn't work as sustained skill

i'm tryin to generate power charges using bonestorm skill and voll's protector equipped. the armor says 25% chance to gain a power charge on critical hit. the skill says it has maximum of 20 projectiles per cast and since it's tagged as sustained skill each projectile have their own crit roll and counts as individual hits. this should mean i can generate more than 1 power charge per cast if i hit critical with some of the projectiles and they roll the %25 chance of generating power charge. and i know i'm hitting most of it as critical cuz i'm using malice and i have decent crit chance. i played couple of hours with this setup and i NEVER generated more than 1 power charge per one bonestorm cast (20 projectiles most of it is crit). i think there's something wrong here if i'm wrong please enlighten me or look into this and fix it asap pls tysm.

am i the only one who noticed this?

I noticed the same !